System and method of determining maximum power point tracking for a solar power inverter

ABSTRACT

A system and method for operating a photovoltaic element at or near a maximum power point. A maximum power point tracker changes a voltage or current set point of a photovoltaic element in sequential discrete steps, measuring an output power at each step after a predetermined settling time. A slope of a power-voltage curve is then estimated and the slope is corrected for irradiance changes. Finally, an operating voltage or current of the photovoltaic element is adjusted based on the slope of the power-voltage curve and other factors, causing the photovoltaic element to operate at or near its maximum power.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.12/616,763, filed on Nov. 11, 2009, now U.S. Pat. No. 7,960,863 whichclaims the benefit of U.S. Provisional Patent Application No.61/113,555, filed on Nov. 11, 2008, both of which are incorporatedherein by reference.

TECHNICAL FIELD

The present disclosure is directed to system and methods of determiningthe maximum power point for solar power systems.

BACKGROUND

Solar power has become an increasingly important energy source for theworld. But like many other forms of energy, electricity produced byphotovoltaic power systems is a scarce and valuable resource. Althoughsolar power is renewable and pollution free, fixed costs associated withgenerating solar power are high. To provide more of a scarce resourceand to offset these high fixed costs, a solar power system shouldoperate to maximize its power output when possible.

Photovoltaic power systems generate power by converting solar energyinto electricity. Solar panels containing photovoltaic cells aretypically arranged in an array and constructed at a location thatreceives plentiful sunshine. Photons from the sun create a voltage inthe photovoltaic cells, which produce a direct current when connected toa load. Oftentimes, the direct current is converted into an alternatingcurrent so that the solar array may provide electricity to a power grid.

A solar array generates maximum power when its photovoltaic cellsoperate where dI/dV=−I/V, which occurs when the instantaneous slope ofthe array's power-voltage curve is equal to zero. This maximum powerpoint may vary with solar irradiance and other factors, such as ambienttemperature. Maximum power point tracking (MPPT) methods attempt todetermine this ideal operating point and adjust how the solar arrayoperates so that the photovoltaic cells take full advantage of availablesolar energy.

The most widely adopted MPPT methods track a solar array'spower-maximizing point reasonably well when solar irradiance and ambienttemperature do not vary quickly with time. However, these methods haveconsiderable drawbacks, including relatively poor performance underdynamic conditions. One existing MPPT method is the perturb and observemethod, in which the operating voltage or current of an array isadjusted and the power output is observed to determine whether thechange results in more power. Although the perturb and observe methodmay operate the solar array near its maximum power point when irradianceis constant, the solar array's operating power generally oscillatesaround the maximum power point as the solar array's operating voltage orcurrent is periodically perturbed to determine whether another pointmaximizes power output. Additionally, during rapidly varying irradiancelevels, this method may react too slowly to successfully determine themaximum power point and may even track in the wrong direction.

Another existing MPPT method is the incremental conductance method inwhich a solar array's power-voltage curve is observed and a maximumpower point is found by comparing the solar array's instantaneousconductance (IV) with an incremental conductance (dI/dV). If the solararray experiences a change in current, its operating voltage is adjusteduntil dI/dV=−I/V once again. The incremental conductance method improvesupon the perturb and observe method in that it does not oscillate aroundthe maximum power point during steady-state operation. However,measuring incremental conductance takes a finite amount of time, duringwhich changes in irradiance may cause the solar array to operate belowits maximum power point. As with the perturb and observe method andother MPPT methods, the incremental conductance method does not optimizea solar array's power output when it is unable to accurately track thesolar array's maximum power point.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a representative system for generating solarpower in accordance with an embodiment of the technology.

FIG. 2 is a block diagram of a system for operating a photovoltaicelement at or near its maximum power point in accordance with anembodiment of the technology.

FIG. 3 is a block diagram of functional components of a system foroperating a photovoltaic element at or near its maximum power point inaccordance with an embodiment of the technology.

FIG. 4 is a flow diagram illustrating a method performed by a system foroperating a photovoltaic element at or near its maximum power point inaccordance with an embodiment of the technology.

DETAILED DESCRIPTION A. Overview

A system and method are described for operating a photovoltaic (PV)element, such as a solar array, solar panel, or portion thereof, at ornear its maximum power point under both static and dynamic conditions.In some embodiments, a maximum power point tracker changes a voltage orcurrent set point of a solar array in sequential discrete steps andmeasures an output power at each step after a predetermined settlingtime. A slope of a power-voltage curve is then estimated and the slopeis corrected for irradiance changes. Finally, an operating voltage ofthe solar array is adjusted based on the slope of the power-voltagecurve and other factors, such that the solar array operates at or nearits maximum power output.

In some embodiments, a maximum power point tracker measures a firstpower of a solar array at a first voltage, measures a second power ofthe solar array at a second voltage that is lower than the firstvoltage, measures a third power of the solar array at the first voltageonce again, measures a fourth power of the solar array at a thirdvoltage that is higher than the first voltage, and measures a fifthpower of the solar array at the first voltage. The maximum power pointtracker may measure the first power, the second power, the third power,the fourth power, and the fifth power at various time intervals so thatthe third power is measured at a time that is central difference fromthe time that the first power and the fifth power are measured and fromthe time that the second power and the fourth power are measured.

Using these first through fifth power measurements, the maximum powerpoint tracker calculates an irradiance-rate-corrected slope of apower-voltage curve associated with the solar array. An operatingvoltage of the solar array is adjusted as a function of theirradiance-rate-corrected slope of the power-voltage curve. Adjustingthe operating voltage of the solar array alters the solar array'soperating current so that the solar array operates at or near itsmaximum power point. In some embodiments, the solar array operates atits maximum power point by adjusting an impedance of the solar array. Inother embodiments, the solar array operates at its maximum power pointby adjusting an operating current of the solar array. In someembodiments, the operating voltage of the solar array is adjusted basedon a change in irradiance between when the first power of the solararray is measured and the fifth power of the solar array is measured.

In some embodiments, the difference between the first voltage and thesecond and third voltages is a function of at least one of power,voltage, irradiance, temperature, environment data, and otherparameters, conditions, or the like. Similarly, in some embodiments, theoperating voltage of the solar array is a function of theirradiance-rate-corrected slope of the power-voltage curve and at leastone of power, voltage, irradiance, temperature, environment data, orother parameters, conditions, or the like.

The system and method will now be described with respect to variousembodiments. The following description provides specific details for athorough understanding of, and enabling description for, theseembodiments of the system and method. However, one skilled in the artwill understand that the system may be practiced without these details.In other instances, well-known structures and functions have not beenshown or described in detail to avoid unnecessarily obscuring thedescription of the embodiments of the system.

It is intended that the terminology used in the description presentedbelow be interpreted in its broadest reasonable manner, even though itis being used in conjunction with a detailed description of certainspecific embodiments of the system. Certain terms may even be emphasizedbelow, however, any terminology intended to be interpreted in anyrestricted manner will be overtly and specifically defined as such inthis Detailed Description section.

B. Embodiments of Maximum Power Point Trackers and Associated Methods

FIG. 1 is a diagram of a representative system 100 for generating solarpower, in which a maximum power point tracker according to the presenttechnology operates. A solar array 110 consists of multiple solar panels120 containing multiple solar cells. The solar cells convert solarenergy into a voltage that creates direct current electricity whenconnected with a load. The solar array 110 and the solar cells composingthe solar array may be of any type, including crystalline,polycrystalline, amorphous, and thin-film.

An inverter 130 connects the solar array 110 with a power grid. Theinverter 130 converts direct current from the solar cells intoalternating current suitable for the power grid. The inverter 130 mayalso control the operating power of the solar array 110 by adjusting animpedance to regulate the solar array's operating voltage or current.One skilled in the art will appreciate that an inverter may control theoperating power of a very large solar array consisting of many solarpanels, or the inverter may control the operating power of a singlesolar panel or a portion thereof. However, as explained below, acomponent other than an inverter may control the operating power of thesolar array 110. For example, a component may be deployed on each solarpanel 120 to independently control the operating voltage or current fromindividual solar panels. Thus, as described herein, a maximum powerpoint tracker may act independently from an inverter to control theoperating voltage or current of a solar panel or solar array. Moreover,although some embodiments are described with respect to controlling anoperating voltage or current of a solar array, one skilled in the artwill appreciate that a maximum power point tracker may just as wellcontrol an operating voltage or current of an individual solar panel, ora portion thereof.

FIG. 2 is a block diagram of a system 200 for tracking a maximum powerpoint of a PV element. A maximum power point tracker 210 determines anoperating voltage and/or current for the PV element that will cause thePV element to operate at or near its maximum power point. The maximumpower point tracker 210 includes a memory and at least one processor,such as an imbedded digital signal processor (DSP), a microcontroller, ageneral purpose processor, or the like. The maximum power point tracker210 measures the power from the PV element, such as one or more solarpanels or arrays, and calculates an operating voltage or current of thePV element to maximize the power output.

A photovoltaic control component 220 is connected with the maximum powerpoint tracker 210 and may control an operating voltage or current of thePV element. The photovoltaic control component 220, for example, maycontrol an impedance that may be adjusted to maximize the output powerof the PV element. The photovoltaic control component 220 may includesemiconductor switches and/or other circuitry that may be adjusted toimpede an output current of the PV element.

In one embodiment, the photovoltaic control component 220 is aninverter. One skilled in the art will appreciate that a maximum powerpoint tracker 210 may be (a) centralized in an inverter, (b) distributedbetween the inverter and another system component, and/or (c)centralized in a system component external to the inverter ordistributed between multiple external system components or anothersystem.

The maximum power point tracker 210 may include one or morecommunication components used for wired or wireless communicationprotocols, such as GSM, CDMA, GPRS, EDGE, UMTS, IEEE-1284, IEEE 802.11,IEEE 802.16, etc. The maximum power point tracker 210 may communicatewith a server 250 or other computing devices via a public and/or privatenetwork 240. The server 250 may access data storage areas 260 to obtainor store data. The maximum power point tracker 210 may receiveenvironment or weather data from the server 250 or from other computingdevices via the public and/or private network.

An environment monitoring component 230 provides environment data to themaximum power point tracker 210. The environment monitoring componentmay include one or more communication components used for wired orwireless communication, such as GSM, CDMA, IEEE-1284, IEEE 802.11, etc.The environment monitoring component may communicate directly with themaximum power point tracker 210 via radio signals or a wired connection,or it may communicate through a mobile telecommunications network orother wireless telecommunications network or wireless local area network(WLAN). The environment monitoring component 230 may include athermometer, a wind gauge, a barometer, a radar system, a satelliteimagery system, a camera, an irradiance sensor, or any other device orsystem that can provide environmental data to the maximum power pointtracker.

In some embodiments, the maximum power point tracker 210 is configuredto process data or signals from the environment monitoring component230. For example, in some embodiments, the environment monitoringcomponent may include a video camera that captures images of the sky.The maximum power point tracker may receive encoded video data from thevideo camera and process the video data to determine, for example, acloud density of the sky or irradiance on the PV element.

FIG. 3 is a block diagram of the maximum power point tracker 210 thattracks a maximum power point of a PV element. The maximum power pointtracker 210 includes a power tracking module 312, a PV element controlmodule 314, and, in some embodiments, an environment input module 316.The power tracking module 312 measures the operating power, voltage,and/or current of the PV element. The power tracking module 312 usesthis data, and in some embodiments, data from the environment inputmodule 316, to calculate an operating voltage or current for the PVelement so that the PV element operates at or near a maximum powerpoint.

The photovoltaic element control module 314 generates control signals tocontrol an operating voltage or current of the PV element. The controlsignals may instruct an inverter or another component to increase ordecrease an impedance, which may alter the operating voltage or currentof the PV element.

The environment input module 316 calculates how environmental conditionsassociated with the PV element affect the maximum power point of the PVelement. The environment input module 316 may monitor environmentalconditions by analyzing images and video of an environment of the PVelement. It may also analyze satellite and radar images and video, windspeed, barometric pressure, temperature, longitude and latitudecoordinates of the PV element, time of day or year, and the like. Thepower tracking module 312 may use environmental data produced by theenvironment input module 316 to track the PV element's maximum powerpoint, as explained in more detail below with reference to FIG. 4.

FIG. 4 is a flow diagram of a process 400 implemented by a maximum powerpoint tracker to operate a PV element at or near a maximum power point.In some embodiments, the process 400 is repeated continuously to trackthe maximum power of the PV element over time. In other embodiments, theprocess 400 is repeated less frequently. The frequency by which theprocess 400 is repeated may depend on a number of factors, includingenvironment data such as a weather forecast. For example, the process400 may be repeated on an hourly basis if a weather forecast predictsconstant sunshine for a PV element's environment, but the process may berepeated at 20 second intervals if the weather forecast predicts partlycloudy skies. In some embodiments, the process 400 is repeated when anoperating parameter of the PV element changes, or because of a change inan environment of the PV element.

At a block 410, the maximum power point tracker controls an operatingparameter (e.g., a voltage set point) of the PV element at a voltage V,and it measures a first power of the PV element after a predeterminedsettling and averaging time. Because of the relationship between voltageand current in Ohm's law, at each step in the process 400 that themaximum power point tracker adjusts or calculates an operating parameterof the PV element, the maximum power point tracker may adjust either anoperating voltage of the PV element or an operating current of the PVelement (i.e., a current set point). Thus, throughout this disclosure,an operating current and an operating voltage are operating parametersthat may be monitored, controlled, and adjusted. In some embodiments,the operating parameters are controlled and adjusted by controlling oradjusting an impedance related to the PV element.

At a block 420, the maximum power point tracker adjusts the operatingparameter of the PV element to a voltage equal to V−V_(dither). Themaximum power point tracker then measures a second power of the PVelement after a predetermined settling and averaging time. Dithervoltage, V_(dither), may be a function of a fill factor of the PVelement, power, voltage, current, irradiance, temperature, time,location, or any other parameters related to the PV element. V_(dither)may also vary depending on a type of solar cell used in the PV element.For example, a large V_(dither) value may be used when a fill factor ofa PV element is high, and a smaller V_(dither) value may be used when afill factor of a PV element is low. V_(dither) may also be manuallycontrolled. In other embodiments a variable dither voltage may be usedto maximize energy harvest, increase a tracking speed of the maximumpower point tracker, and improve stability of the maximum power pointtracker. For example, if a PV element receives a constant irradiance,V_(dither) may be reduced to a nominal value or to zero to avoidoscillating an operating power of the PV element around the PV element'smaximum power point. In some embodiments, V_(dither) is has a negativevalue, and the steps in the process 400 may be changed accordingly. Inembodiments where the operating parameter is an operating current of aPV element, a dither current, I_(dither), may be used instead of adither voltage.

At a block 430, the maximum power point tracker adjusts the operatingparameter of the PV element to voltage V. The maximum power pointtracker then measures a third power of the PV element after apredetermined settling and averaging time. At a block 440, the maximumpower point tracker adjusts the operating parameter of the PV element toa voltage equal to V+V_(dither). The maximum power point tracker thenmeasures a fourth power of the PV element after a predetermined settlingand averaging time. In some embodiments, the value of V_(dither) atblock 440 is different from the value of V_(dither) at block 420. At ablock 450, the maximum power point tracker adjusts the operatingparameter of the PV element to voltage V. The maximum power pointtracker then measures a fifth power of the PV element after apredetermined settling and averaging time. In some embodiments, themaximum power point tracker measures a power of the PV element at avalue of the operating parameter equal to V−V_(dither) and V+V_(dither)at blocks 410 and 450, respectively, and it measures a power of the PVelement at a value of the operating parameter equal to V at blocks 430and 450.

In some embodiments, the maximum power point tracker measures the powerof the PV element at blocks 410-450 in equal time intervals. In otherembodiments, the maximum power point tracker measures the power of thePV element at blocks 410-450 at varying time intervals. The duration ofthe time intervals between power measurements in blocks 410-450 maydepend on numerous factors, including the operating power, voltage, orcurrent of the PV element. Additionally or alternatively, the durationof the time intervals may depend on a PV element's historical or recentpower output, irradiance, time, or other conditions.

At a block 460, the maximum power point tracker calculates anirradiance-rate-corrected slope of a power-voltage curve of the PVelement. In embodiments that the power is measured at blocks 410-450 inequal time intervals and the value of V_(dither) at block 420 is equalto the value of V_(dither) at block 440, the irradiance-rate-correctedslope can be calculated using the following equation:

$\begin{matrix}{\frac{\mathbb{d}P}{\mathbb{d}V} = \frac{P_{4} - P_{2} - {\left( {P_{5} - P_{1}} \right)/2}}{2*V_{dither}}} & (1)\end{matrix}$where P₄ is the power calculated at block 440, P₂ is the powercalculated at block 420, P₅ is the power calculated at block 450, P₁ isthe power calculated at block 410, and V_(dither) is the dither voltageof blocks 420 and 440. The process 400 may be central difference about acommon time point, meaning that a time interval between measuring P₁ atblock 410 and measuring P₃ at block 430 is equal to a time intervalbetween measuring P₃ at block 430 and measuring P₅ at block 450, and atime interval between measuring P₂ at block 420 and measuring P₃ atblock 430 is equal to a time interval between measuring P₃ at block 430and measuring P₄ at block 440. In some embodiments, the process 400 mayinclude more or fewer power measurements at varying operating parametersof the PV element. In such embodiments, the maximum power point trackermay still measure power of the PV element so that the power measurementsare central different about a common time point. In some embodiments,such as when the value of V_(dither) at block 420 is not equal to thevalue of V_(dither) at block 440 or when time intervals between powermeasurements at blocks 410-450 are not equal, theirradiance-rate-corrected slope may be calculated using other equations.In some embodiments, the maximum power point tracker calculates apower-current curve of the PV element, and the maximum power pointtracker calculates an irradiance-rate-corrected slope of thepower-current curve.

At a block 470, the maximum power point tracker adjusts the operatingparameter of the PV element. The operating parameter of the PV elementmay be adjusted by changing an impedance using a Newton or shootingmethod. The impedance is adjusted as a function of theirradiance-rate-corrected slope of the PV element's power-voltage curve.This is equivalent to adjusting the operating voltage of the PV elementto a new nominal voltage V′. Nominal voltage V′ may be calculated usingvarious equations and/or conditional statements, including, for example,one or more of the following:

$\begin{matrix}{{{{{if}\mspace{14mu}\frac{\mathbb{d}P}{\mathbb{d}V}} > 0},\mspace{14mu}{V^{\prime} = {V + {V_{{step}\; 1}*\left( {1 + {C_{2}*\frac{\left( {P_{\max} - P_{n}} \right)}{P_{\max}}}} \right)*\frac{\mathbb{d}P}{\mathbb{d}V}}}}}{{{else}\mspace{14mu} V^{\prime}} = {V - {V_{{step}\; 2}*\left( {1 + {C_{2}*\frac{\left( {P_{\max} - P_{n}} \right)}{P_{\max}}}} \right)*\frac{\mathbb{d}P}{\mathbb{d}V}}}}} & (2) \\{{{{{if}\mspace{14mu}\frac{\mathbb{d}P}{\mathbb{d}V}} > 0},\mspace{14mu}{V^{\prime} = {V + {V_{{step}\; 3}*\left( {1 + {C_{2}*\frac{\left( {P_{\max} - P_{n}} \right)}{P_{\max}}}} \right)}}}}{{{else}\mspace{14mu} V^{\prime}} = {V - {V_{{step}\; 4}*\left( {1 + {C_{2}*\frac{\left( {P_{\max} - P_{n}} \right)}{P_{\max}}}} \right)}}}} & (3) \\{{{{{if}\mspace{14mu}\frac{\mathbb{d}P}{\mathbb{d}V}} > 0},\mspace{14mu}{V^{\prime} = {V + V_{{step}\; 5}}}}{{{else}\mspace{14mu} V^{\prime}} = {V - V_{{step}\; 6}}}} & (4) \\{V^{\prime} = {V + {C_{1}*V_{{step}\; 7}*\frac{\mathbb{d}V}{\mathbb{d}P}}}} & (5)\end{matrix}$where C₁ and C₂ are variables that may, for example, be used as a gainsetting or a scale factor; P_(max) is a maximum power of the PV element;P_(n) is a current power output of the PV element at operating voltageV; and V_(step1), V_(step2), V_(step3), V_(step4), V_(step5), V_(step6),and V_(step7) are each a voltage “step size”, affecting both themagnitude and direction that the PV element's operating voltage isadjusted. V_(step1), V_(step2), V_(step3), V_(step4), V_(step5),V_(step6), and V_(step7) may be variables, and may be functions ofpower, voltage, irradiance, temperature, time, or any other parameterassociated with the PV element. For example, V_(step5) and V_(step6) mayvary according to an observed power change, weather data, or irradiance.After V′ is calculated, it may be bounded to prevent the maximum powerpoint tracker from generating a command that the PV element is incapableof achieving.

In some embodiments, the process 400 further includes an optional stepof receiving environment data. Environment data may include atemperature, a barometric pressure, a weather forecast (includingreal-time forecasts and predictions based on weather conditions of aprior day), a radar or satellite image or video, a thermal image, aphotograph or video, or any other data related to the PV element'senvironment. The maximum power point tracker may directly adjust or tuneits method of determining a maximum power point of the PV element basedon the environment data, or it may factor environmental data into thevalue of V_(dither), V_(step1), V_(step2), V_(step3), V_(step4),V_(step5), V_(step6), or V_(step7).

For example, environment data may include real-time cloud covermeasurements or assessments that are related to a location of the PVelement. Cameras mounted near the PV element may capture images of thesky, and the maximum power point tracker may process the images toproduce parameters defining cloud cover, such as cloud spacing, cloudmovement direction, cloud patterns (e.g., wispy, mottled, or solid),cloud optical density, and the like. The maximum power point tracker mayaccount for these parameters by adjusting the value of V_(dither),V_(step1), and V_(step2), or it may adjust the frequency at which theprocess 400 repeats itself, enabling the system to ignore temporaryirradiance changes. As another example, environment data may include aweather forecast that the maximum power point tracker receives over acomputer network, such as the internet. If the weather forecast predictsa cloudless sky, the maximum power point tracker may adjust V_(dither),V_(step1), and V_(step2), or any other variable, accordingly.

In some embodiments, the maximum power point tracker starts operating atsunrise at a voltage equal to an open circuit voltage minus a deltavalue. The delta value is determined parametrically, and may depend on atype of solar cell composing a PV element, environment data, a design ofthe array, temperature, and other factors.

In some embodiments, the maximum power point tracker determines whetheran irradiance of the PV element changes during the process 400. Themaximum power point tracker may compare the power measured at block 430with the power measured at block 410 and block 450. If the powermeasured at block 410 is different from the power measured at block 430,the maximum power point tracker may determine that irradiance of the PVelement changed during the time period between block 410 and block 430.Similarly, if the power measured at block 450 is different from thepower measured at block 430, the maximum power point tracker maydetermine that the irradiance of the PV element changed during the timeperiod between block 430 and block 450. Consequently, the maximum powerpoint tracker may adjust V_(step1), V_(step2), V_(step3), V_(step4),V_(step5), V_(step6), and V_(step7) as necessary to account for changesin irradiance.

In some embodiments, the maximum power point tracker may adjust theparameters used to calculate an operating voltage of a PV elementdepending on the PV element's composition. For example, a maximum powerpoint tracker may vary parameters used to calculate an operating voltagefor a PV element composed of crystalline solar cells from thoseparameters that are used to calculate an operating voltage for a PVelement composed of thin-film solar cells.

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from thespirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

1. A method of setting an operating parameter of a photovoltaic elementusing a maximum power point tracker having a processor and a memory, themethod comprising: operating a photovoltaic element at a value of anoperating parameter of the photovoltaic element; sequentially changingthe value of the operating parameter of the photovoltaic element indiscrete steps; measuring a power of the photovoltaic element atmultiple values of the operating parameter, wherein the multiple valuesof the operating parameter include the values of the operating parameterafter each discrete step of sequentially changing the value of theoperating parameter; calculating a slope of a power-operating parametercurve of the photovoltaic element using the power of the photovoltaicelement measured at the multiple values of the operating parameter;calculating a new set value of the operating parameter of thephotovoltaic element, wherein the new set value of the operatingparameter is based at least in part on one of the multiple values of theoperating parameter; and adjusting the value of the operating parameterof the photovoltaic element so that the value of the operating parameterof the photovoltaic element is equal to the new set value of theoperating parameter.
 2. The method of claim 1, wherein the multiplevalues of the operating parameter include the value of the operatingparameter before sequentially changing the value of the operatingparameter of the photovoltaic element in discrete steps.
 3. The methodof claim 2, wherein the new set value of the operating parameter isbased at least in part on the value of the operating parameter beforesequentially changing the value of the operating parameter of thephotovoltaic element in discrete steps.
 4. The method of claim 2,wherein the operating parameter of the photovoltaic element is a currentor a voltage.
 5. The method of claim 1, wherein the new set value of theoperating parameter is based at least in part on a change in irradianceon the photovoltaic element.
 6. The method of claim 1, furthercomprising receiving environment data, wherein the new set value of theoperating parameter of the photovoltaic element is based at least inpart on the environment data.
 7. The method of claim 1, whereinsequentially changing the value of the operating parameter of thephotovoltaic element in discrete steps comprises changing the value ofthe operating parameter by an amount for each discrete step that isbased at least in part on a power of the photovoltaic element measuredat the value of the operating parameter before sequentially changing thevalue of the operating parameter of the photovoltaic element in discretesteps.
 8. The method of claim 1, wherein sequentially changing the valueof the operating parameter of the photovoltaic element in discrete stepscomprises changing the value of the operating parameter by an amount foreach discrete step that is determined based at least in part on a fillfactor or a type of solar cell included in the photovoltaic element. 9.The method of claim 1, wherein measuring the power of the photovoltaicelement at multiple values of the operating parameter comprisesmeasuring the power of the photovoltaic element after equal timeintervals.
 10. The method of claim 1, wherein the value of the operatingparameter of the photovoltaic element prior to sequentially changing thevalue of the operating parameter of the photovoltaic element in discretesteps is equal to a value of an open circuit voltage of the photovoltaicelement minus a delta value.
 11. A maximum power point tracking systemfor maximizing a photovoltaic element's output power, the systemcomprising: a photovoltaic element control component that controls anoperating parameter of a photovoltaic element, wherein the photovoltaicelement control component is configured to: operate the photovoltaicelement at a value of an operating parameter of the photovoltaicelement; sequentially change the value of the operating parameter of thephotovoltaic element in discrete steps; and adjust the value of theoperating parameter of the photovoltaic element so that the value of theoperating parameter of the photovoltaic element is equal to a new setvalue of the operating parameter; and a maximum power point trackingcomponent, wherein the maximum power point tracking component isconfigured to: measure a power of the photovoltaic element at multiplevalues of the operating parameter, wherein the multiple values of theoperating parameter include the values of the operating parameter aftereach discrete step of the value being sequentially changed; calculate aslope of a power-operating parameter curve of the photovoltaic elementusing the power of the photovoltaic element measured at the multiplevalues of the operating parameter; and calculate the new set value ofthe operating parameter of the photovoltaic element, wherein the new setvalue of the operating parameter is based at least in part on one of themultiple values of the operating parameter.
 12. The system of claim 11,wherein the multiple values of the operating parameter include the valueof the operating parameter before being sequentially changed in discretesteps.
 13. The system of claim 12, wherein the new set value of theoperating parameter is based at least in part on the value of theoperating parameter before being sequentially changed in discrete steps.14. The system of claim 11, wherein the operating parameter of thephotovoltaic element is a current or a voltage.
 15. The system of claim11, wherein the new set value of the operating parameter is based atleast in part on a change in irradiance on the photovoltaic element. 16.The system of claim 11, further comprising an environment sensingcomponent, the environment sensing component configured to produce orreceive environment data, wherein the new set value of the operatingparameter of the photovoltaic element is based at least in part on theenvironment data.
 17. The system of claim 11, wherein the amount of eachsequential change of the value of the operating parameter is based atleast in part on a power of the photovoltaic element measured at thevalue of the operating parameter prior to the value being sequentiallychanged in discrete steps.
 18. The system of claim 11, wherein theamount of each sequential change of the value of the operating parameteris determined based at least in part on a fill factor or a type of solarcell included in the photovoltaic element.
 19. The system of claim 11,wherein the maximum power point tracking component is further configuredto measure the power of the photovoltaic element after equal timeintervals.
 20. The system of claim 11, wherein the value of theoperating parameter of the photovoltaic element prior to beingsequentially changed in discrete steps is equal to a value of an opencircuit voltage of the photovoltaic element minus a delta value.